About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Abstract

Recent demonstrations have shown that by creating a periodic surface corrugation about a single subwavelength aperture, the transmission can be enhanced at wavelengths related to the periodicity. We demonstrate that by varying the phase of the surface corrugation relative to the single subwavelength aperture, dramatic variations can be made in the transmission resonance lineshape at THz frequencies, ranging from transmission enhancement to transmission suppression. This finding is particularly surprising, since the nearly exclusive focus of published work has been on understanding and optimizing the enhancement process in these and associated structures. We present a simple model that qualitatively explains our observations. This represents, we believe, a first step in fully controlling the spectral transmission properties of these structures.

Figures (4)

Schematic representation of the corrugation geometry of the bullseye structures relative to the central aperture. (A) Photograph of a typical in-phase bullseye structure used in the experiment. (B) Cross-sectional line diagrams of the four bullseye structures. The surface corrugation pattern in these structures is shifted relative to one another by a phase of π/2. The dotted lines in (B) represent the location of the circular aperture. The grooves in each structure have square cross-section. In all experiments, the THz pulses were incident on the corrugated surface at normal incidence.

Experimentally observed time-domain waveforms and corresponding amplitude spectra for the structures shown in Fig. 1. (a) Five time domain waveforms. The top trace corresponds to a bare aperture. The lower four traces correspond to the four bullseye structures. (b) The amplitude spectra obtained by Fourier transforming the time-domain waveforms. In each case, the spectra were normalized to the peak transmission value in an equivalently thick bare aperture.

Numerical simulations of time-domain waveforms and corresponding amplitude spectra. (a) Five time-domain waveforms. The top trace consists of a single cycle pulse, i.e., the principal pulse, which corresponds to the non-resonant transmission through a bare aperture. The lower four traces consist of a superposition of the single cycle pulse and a damped sinusoid. The phase difference between the single cycle pulse and the sinusoids is 0, π/2, π, and 3π/2, respectively. (b) The amplitude spectra obtained by Fourier transforming the time-domain waveforms. The simulation results are in good qualitative agreement with the experimental results shown in Fig. 2.

Effect of offsetting the aperture from the center for the in-phase bullseye structure. (A) Cross-sectional line diagrams of the aperture placement. In each structure, the apertures were successively moved 0.25 mm further from the center corresponding to 0, 0.25, 0.5, 0.75, and 1 mm from the center. The dotted lines in (a) represent the location of the circular aperture. The grooves in each structure have square cross-section. (b) The amplitude spectra obtained by Fourier transforming the measured time-domain waveforms. In each case, the spectra were normalized to the peak transmission value in an equivalently thick bare aperture.